In the case of a multi-carrier transmission scheme based on OFDM, the effects of transmission channels on carriers that are allocated for each frequency differ by carriers. Due to this reason, a receiving side estimates each channel status with a signal that is transmitted through each carrier, and represents the estimated information as a certain value to refer to the information as CSI. Since the usability of the CSI estimated by the receiving side through the above-described operation is diverse, a method has been proposed where in the case of wireless communication, a receiving side retransmits CSI to a transmitting side and the transmitting side may enable the transmission of a transmitted signal that is adjusted on the basis of the retransmitted CSI, and when it is impossible to retransmit CSI like wireless broadcasting, received information may more accurately be decoded by using the estimated CSI in adjusting the error of a received signal. The present invention proposes a method that requires a smaller memory capacity and simpler hardware configuration than the existing method, in a case where a receiving side uses a received signal as additional adjustment information for decoding in the above-described method for using CSI.
FIG. 1 is a block diagram illustrating a typical decoder transfer apparatus for CSI and soft-decided signal. As a method of using CSI for more accurate decoding, a method is used which transfers a CSI value estimated and a soft-decided signal received to a decoder and applies them to the decoder.
Typical technologies have been disclosed in U.S. Pat. No. 7,492,830, U.S. Pat. No. 7,272,294 and U.S. Pat. No. 5,313,495.
To provide a more detailed description on the typical technologies, for example, a method will be described below for enhancing the decoding performance of a viterbi decoder well-known as a representative decoder by using CSI.
To provide a description on the internal structures of most typical receivers for easy understanding, the viterbi decoder is not disposed at the direct rear end of a soft-decision block for an actually-received signal but is disposed at the rear ends of several function blocks based on a memory.
The above-described typical technology should process a function block using a memory device such as a de-interleaver that exists between the viterbi decoder and a soft-decision block for a received signal for transferring the received signal and CSI to the viterbi decoder. In this case, an additional memory is required for storing CSI, and moreover, the speed of a clock for transmitting the received signal and CSI should be higher.
Furthermore, the typical method cannot appropriately perform adjustment suitable for a soft-decided signal in applying pre-estimated CSI to a decoder.